1. Field of the Invention
The present invention relates to a hydrodynamic bearing unit, an optical deflector, an optical scanner, and an image forming apparatus in which easy assembling is provided, oil-leakage is prevented, and high accuracy is achieved.
2. Description of the Related Art
A conventional optical deflector used in an optical scanner has, as disclosed in Japanese Patent Application Publication No. 2002-139041, a structure in which a bearing member has an end portion, which is disposed adjacent to an opening of a housing and in which an annular oil accumulation portion is provided, and another end which is fixed on the housing with an adhesive.
On the other hand, Japanese Patent Application Publication No. 2005-92129 discloses an optical deflector of an optical scanner in which mirrors are downsized and rotated at high rotational speed, that is, about 50,000 to 60,000 rpm. Due to structures disclosed in Japanese Patent Application Publication No. 2005-92129, mirrors are downsized and a bearing dimension is reduced in size and diameter so that bearing loss is reduced. Thereby, high rotational speed over 60,000 rpm can be achieved. However, it is difficult to fix the bearing on the housing with adhesives, and therefore assembly is remarkably degraded.
To solve the above problems, as disclosed in Japanese Patent Application Publication No. 2002-139041, it is proposed that the bearing member is disposed in a close contact state with the sealing member to fix the bearing member onto the housing. However, in this case, there is a possibility of oil-leakage occurring.